Uh... no. Disregard KM's answer as that is NOT how this works. A game is either fully rendered in 1080p or it isn't. It's not an upgraded setting or a selectable option, as you mistakenly believe. What you saw on the back of the box was a trick, of sorts, that developers use to hook a lot of unknowledgeable people. You see 1080p and go "Ooh, that says 1080p! I think that means the game looks good!"

The trick? Only certain parts, namely cutscenes, are rendered in 1080p, the rest is 720. Almosr no one renders full games in 1080p because it's extremely time and cost prohibitive. You'll find PSN downloadable games that are fully 1080p, and the occasional full PS3 game, but that's about it.